Microcystis sp. Identification

Description

Forms
clusters
of cells (colonies) which may be spherical, lobed or an extensive reticulate
mass. Suspended colonies often appear as small blue-green "clots" to the unaided
eye. Individual cells are very small (3-5 mm diameter) with conspicuous, highly
refractive pseudovacuoles that cause the colonies to be buoyant and float to
surface. Cells of a colony are held together by a transparent, gelatinous matrix
which may be difficult to discern under microscopic examination. Akinetes and
heterocysts are absent. The photograph is the copyright property of Dr. Robin
Matthews, Western Washington University, and used with her permission.

This organism is known to produce a family of toxins called microcystins.
Named after this genus, they are heptapeptides that primarily affect the liver
in animals (hepatotoxins). Current evidence suggests that the toxins alter the
cytoskeletal components of hepatocytes leading to intercellular dissociation of
hepatocytes causing blood accumulation within the liver and death by hypovolumic
shock. Very recent experimental evidence shows that at least one of the
molecular mechanisms of action is consistent with certain known carcinogens.
This information has led researchers to suspect these toxins as liver
carcinogens, which could prove significant to humans following continuous, low
level exposure.

Poisoning symptoms in animals

Symptoms may take 30 minutes to 24 hours to appear, depending upon the size
of the animal affected and the amount of toxic bloom consumed. Microcystin
toxicosis may include jaundice, shock, abdominal pain/distention, weakness,
nausea/vomiting, severe thirst, rapid/weak pulse, and death.

Acknowledgements

This information is from "Toxic Cyanobacterial Blooms - A
Field/Laboratory Guide". This guide was written by Dr. M. A. Crayton from
Pacific Lutheran University, Tacoma, Washington and edited by Dr. F. Joan Hardy,
Washington State Department of Health. Used with permission.